The present invention relates to endless belts, particularly to an endless belt having power transmission surfaces exhibiting high wear resistance, and more particularly to a timing belt jacket fabric coated with a material which exhibits improved wear resistance and lubricity, as well as to a method for producing such belts.
It is known to provide an endless power transmission belt construction having an inner longitudinal surface, an outer longitudinal surface and opposed side edges, wherein the outer surface of the belt is a substantially flat surface and the inner surface of the belt is defined by a plurality of longitudinally disposed and alternately spaced apart projections and grooves. Such endless belts such as toothed belts are commonly used in high temperature, high speed and high load environments associated with various industrial and automotive drive systems. In the automotive area, various factors have contributed to the growing demand for such belts that perform under increasingly high loads and temperatures which ordinarily reach 120° C. to 140° C. under high load and high speed. It is common for the surfaces of the spaced apart projections and grooves to deteriorate when exposed to such conditions over time.
In recent years, performance characteristics of endless belts, such as minimal frictional heat generation, quiet operation, dimensional stability and high temperature performance, have become increasingly important in automotive original equipment and aftermarket applications. With respect to endless toothed belts in particular, frictional heat generation and heat build-up reduce the efficiency of the belt, and the higher operating temperatures frequently encountered by the belts can reduce belt life considerably by lowering the tear strength and fatigue life of the tooth or by weakening the bonds between the belt components. The use of a wear resistant fabric positioned along the outer sprocket-engaging face of the belt has been used to reduce the excessive wear problem. The improvement realized, however, has not proved to be completely satisfactory. Other attempts to improve the wear resistance of the belts have included the use of an elastomer impervious material, such as polyethylene bonded to one side of the wear-resistant fabric surface so that during the casting operating the elastomer impervious material seals the outer side only of the fabric and thereby isolates the elastomer from the outer surface of the fabric layer by preventing the fibers on the outermost surface layer from becoming completely encapsulated by elastomer. While polyethylene has been used with moderate success for many years in reducing excess wear on the belt tooth surface, the demands placed on such belts by the present automotive environment requires that belts with even more stringent wear resistant characteristics be developed to meet the need of the industry.
Consequently, there remains an urgent need in the automotive industry to produce an endless belt, including an endless toothed belt which overcomes the inadequacies of prior constructions, does not experience significant frictional heat generation and which otherwise remains dimensionally stable throughout its life.